1. Technical Field
The present invention relates to a liquid container suitable for detecting an amount of remaining liquid (ink) in a liquid consuming apparatus such as an inkjet printing apparatus and a method of manufacturing the liquid container.
2. Related Art
As a representative example of a liquid consuming apparatus, there is an inkjet printing apparatus having an inkjet print head for printing an image. Other liquid ejecting apparatuses may include an apparatus having a coloring material ejecting head used for manufacturing a color filter and the like of a liquid crystal display, an apparatus having an electrode material (conductive paste) ejecting head used for forming electrodes of an organic EL display, a field emission display (FED), and the like, an apparatus having a biological organic material ejecting head used for manufacturing a bio chip, and an apparatus having a sample ejecting head as a precise pipette.
In the inkjet printing apparatus as the representative example of the liquid consuming apparatus, an inkjet print head having a pressure generator pressurizing a pressure generating chamber and nozzle orifices ejecting the pressurized ink as ink droplets is mounted on a carriage. By endlessly supplying the ink in an ink container to the print head through a flow channel, a printing operation can be continuously performed. The ink container is constructed as a detachable cartridge that can be replaced by a user when the ink is completely consumed.
There is a method of managing ink consumption by integrating the number of ink droplets emitted from the print head or the amount of ink sucked in maintenance by software or a method of managing when the ink is actually consumed by a predetermined amount by attaching a liquid level detecting electrode to the ink cartridge, as a method of managing the ink consumption of an ink cartridge.
However, the method of managing the ink consumption by integrating the number of ejected ink droplets or the amount of ink by software causes the following problem. The head may eject ink droplets with non-uniformity in weight. The non-uniformity in weight of the ink droplets does not affect the image quality but the ink with a margin is filled in the ink cartridge in consideration of accumulation of errors in ink consumption due to the non-uniformity. Accordingly, there is a problem that the ink corresponding to the margin remains in some apparatuses.
On the other hand, in the method of managing when the ink is consumed by the use of an electrode, since the actual amount of remaining ink can be detected, it is possible to manage the amount of remaining ink with high reliability. However, since the detection of the ink level depends on the conductivity of the ink, the kinds of ink detectable are limited, thereby complicating the sealing structure of the electrode. Since precious metals with excellent conductivity and anti-corrosion are usually used as the material of the electrode, the cost for manufacturing the ink cartridge is enhanced. Since two electrodes should be necessarily formed, the number of manufacturing processes increases, thereby increasing the manufacturing cost.
Therefore, to solve the above-mentioned problems, a piezoelectric device (herein, referred to as a sensor unit) is disclosed in JP-A-2001-146030. The sensor unit monitors the amount of ink remaining in the ink cartridge by the use of the resonance frequency of a residual vibration signal resulting from the residual vibration (free vibration) of a vibrating plate after forcible vibration when the ink remains and does not remain in a sensor cavity opposed to the vibrating plate having a piezoelectric element formed thereon.
In FIG. 8 of JP-A-2006-248201, plural vertical-direction changing portions changing the flow of ink in vertical directions are shown. The space above the vertical-direction changing portions serves as a bubble trapping space.
In FIGS. 9 and 14 of JP-A-2006-315302, a structure supporting a sensor base at three positions of a partition wall and both main case walls thereof is shown. In JP-A-2001-328277, a barrier wall is disposed in the liquid opposed to the sensor, whereby bubbles hardly enter the sensor cavity even when the bubbles are formed in the liquid level in the tank.
Techniques of securing a bypass channel of a liquid by not welding a part of a film covering an opening of a liquid passage and then closing the bypass channel of the liquid by welding the part of the film are disclosed in JP-A-2005-022257 and JP-A-2004-306466.
The technique disclosed in JP-A-2006-248201 employs a specific gravity separation method of trapping bubbles having small specific gravity in the upside by the use of a labyrinth channel on the basis of a difference in specific gravity between the liquid and the bubbles.
Here, as shown in FIG. 8 of JP-A-2006-248201, the ink is introduced from the lower position of the bubble trapping space and the ink is discharged from the lower position of the bubble trapping space. In this case, as described later, when the ink consumption rate is great due to a continuous printing operation and thus the ink flow rate is great, the bubbles in the bubble trapping space are sucked into the ink and discharged along with the ink in the vicinity of the ink end. Then, bubbles are formed in the buffer chamber in the just upstream side of the sensor cavity and the bubbles are detected by the sensor, thereby falsely detecting the ink end.
In the technique disclosed in JP-A-2006-315302, the vibration of the piezoelectric element is absorbed by the main case coming in contact with the sensor base at three positions, thereby making it difficult to satisfactorily guarantee the vibration being detectable by the piezoelectric element. Since the sensor base is positioned in an opening formed in the main case, bubbles may stay in minute gaps around the sensor base at the time of injecting the ink, thereby causing false detection of the ink end. This problem is not prevented even by the use of the barrier wall shown in JP-A-2001-328277. This is because the barrier wall hinders the flow of ink at the time of initially injecting the ink to easily generate bubbles around the sensor base.